1. Field of the Invention
Embodiments of the present invention generally relate to carbon dioxide blasting. More specifically, embodiments of the present invention relate to cleaning tubulars using solidified carbon dioxide.
2. Description of the Related Art
Tubes are used throughout the chemical industry, generally in applications where heat transfer between one or more fluids inside of a tube and one or more fluids outside of the tube is desired. Typical examples of tubes in use within the chemical processing and refining industries include heat exchanger tubes and tubular reactors. In operation, scale, biological growth, corrosion byproducts or other contaminants can accumulate and/or deposit on the interior surfaces of the tubes. Similarly, reaction byproducts such as sintered catalyst, combustion byproducts, and scale can form or otherwise deposit within the tubes. Regular removal of the built-up deposits (or scale) on the interior surfaces of the tubes is necessary to ensure efficient operation and maximum productivity.
Conventionally, those deposits are removed, i.e. each tube is cleaned, by passing an abrasive device or chemical substance through the bore of the tube to dislodge or otherwise remove the deposits. For example, hydroblasting, sandblasting, and mechanical abrasion techniques have been used to remove deposits and clean the inner surfaces of the tubes. Hydroblasting uses water at pressures up to 40,000 psig. Hydroblasting generates large quantities of wastewater, frequently containing the contaminants removed from the tubes, which require additional treatment prior to disposal or recovery of the water. Sandblasting utilizes a sandblast medium or aggregate that also creates large quantities of solid waste, which requires additional treatment prior to disposal or recovery of the medium. Mechanical abrasion typically involves passing a brush through the tube to physically abrade the deposits from the tube.
However, such physical removal techniques, while effective from removing the unwanted deposits from the tubes, are so physically abrasive that the metal substrate beneath the deposits is actually etched away. Conventional chemical removal techniques can also have the same etching effect on the tubes, and are also extremely difficult to cleanup and discard post-treatment. Removal of the base metal substrate weakens the tubes and increases the likelihood of corrosion and/or structural weaknesses within the tube.
There is a need, therefore, for a removal system that can effectively and efficiently remove unwanted deposits from within a tube without structurally affecting the tube and without generating a large quantity of waste requiring treatment prior to disposal.